2003
FISHERIES OCEANOGRAPHY

Modelling the distribution, sustainability and diapause
emergence timing of the copepod Calanus finmarchicus
in the Labrador Sea

DP Tittensor, B deYoung, C Tang.

Abstract

It is now recognized that Calanus finmarchicus, the
dominant copepod zooplankter of the North Atlantic,
has most of its biomass in the open ocean. While the
Labrador Sea does contain a large population of Calanus finmarchicus, the importance of possible connections with the rest of the North Atlantic are not
understood. Although there are few wintertime
observations, sufficient data exist to model the role of
the circulation, temperature and food supply on population dynamics. This study couples a biological
model of Calanus finmarchicus with a physical
oceanographic model of the Labrador Sea, using
chlorophyll data derived from observations by the
satellite-borne SeaWiFS (Sea-viewing Wide Fieldof-view Sensor) as a proxy food supply for the
numerical copepods. We produce a large-scale, comprehensive picture of the spatial distribution of
Calanus finmarchicus in the Labrador Sea, along with
an exploration of the timing of diapause and an
examination of population sustainability. We are able
to simulate reasonably well the temporal and spatial
patterns of Calanus finmarchicus in the Labrador Sea.
During a year long model run, the population has a
single generation over most of the Labrador Sea, with
a final diapausing population about 50% the size of the
initial for the parameters used in these simulations. A
latitudinally dependent diapause emergence scheme
with early emergence to the south of Newfoundland
provides the best fit to data. A change of 0.5C in the
temperature field can cause significant changes in the
population abundance in a single year, due to changes
in Calanus finmarchicus growth rates.